I. Field
The present disclosure relates generally to the field of image processing and, more specifically, to techniques for auto exposure control that are scene-dependent.
II. Background
Auto Exposure Control (AEC) is the process to automatically adjust exposure time and sensor gain to reach a pleasing/preferred image quality, especially brightness. Most cameras (including camera phones) use a fixed luma target for the AEC adjustment (e.g., to minimize the difference between a frame-luma and a pre-defined luma target). However, psychophysical experiments show that the most preferred images may have a very different luma target. Thus, a fixed luma target does not work well for all scenes.
Currently, most cameras are using a fixed luma target for the AEC adjustment. Some advanced cameras such as digital single-lens reflex (DSLR) or professional cameras have their own proprietary database about setting the exposure level (i.e., EV0). However, even these kinds of cameras do not provide a preferred exposure control based on psychophysical experiments.
Based on psychophysical experiments, a fixed target for AEC adjustment is not an optimal method for such adjustment.
Other cameras may adjust a luma target according to the scene's brightness level. However, this process still does not produce an image to match the human preference.